Some existing proxy services act as intermediaries between user devices and content provider web sites. For example, rather than sending a request for content associated with a web page to the content provider web site, the user device may send the request to a third party proxy service. The third party proxy service obtains the content on behalf of the user device, and may perform compression on the content before sending the content to the user device. The amount of compression varies based on the content being compressed, among other factors. For example, compressed images generally do not compress further without sacrificing image quality. As such, the costs associated with use of the existing proxy services may outweigh the savings in size reduction from the compression. Additionally, the existing proxy services take an all-or-nothing approach to compression by compressing either all the resources or none of the resources.